Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention

FGL2/FcγRIIB Signalling Mediates Arterial Shear Stress-Mediated Endothelial Cell Apoptosis: Implications for Coronary Artery Bypass Vein Graft Pathogenesis

The sudden exposure of venous endothelial cells (vECs) to arterial fluid shear stress (FSS) is thought to be a major contributor to coronary artery bypass vein graft failure (VGF). However, the effects of arterial FSS on the vEC secretome are poorly characterised. We propose that analysis of the vEC secretome may reveal potential therapeutic approaches to suppress VGF. Human umbilical vein endothelial cells (HUVECs) pre-conditioned to venous FSS (18 h; 1.5 dynes/cm2) were exposed to venous or arterial FSS (15 dynes/cm2) for 24 h. Tandem Mass Tagging proteomic analysis of the vEC secretome identified significantly increased fibroleukin (FGL2) in conditioned media from HUVECs exposed to arterial FSS. This increase was validated by Western blotting. Application of the NFκB inhibitor BAY 11-7085 (1 µM) following pre-conditioning reduced FGL2 release from vECs exposed to arterial FSS. Exposure of vECs to arterial FSS increased apoptosis, measured by active cleaved caspase-3 (CC3) immunocytochemistry, which was likewise elevated in HUVECs treated with recombinant FGL2 (20 ng/mL) for 24 h under static conditions. To determine the mechanism of FGL2-induced apoptosis, HUVECs were pre-treated with a blocking antibody to FcγRIIB, a receptor FGL2 is proposed to interact with, which reduced CC3 levels. In conclusion, our findings indicate that the exposure of vECs to arterial FSS results in increased release of FGL2 via NFκB signalling, which promotes endothelial apoptosis via FcγRIIB signalling. Therefore, the inhibition of FGL2/FcγRIIB signalling may provide a novel approach to reduce arterial FSS-induced vEC apoptosis in vein grafts and suppress VGF.

Evaluation of the Patients with Recurrent Angina After Coronary Artery Bypass Grafting

INTRODUCTION

In this study, we aimed to evaluate the most common causes of recurrent angina after coronary artery bypass grafting (CABG) and our treatment approaches applied in these patients.

METHODS

We included all patients who underwent CABG, with or without percutaneous coronary intervention after CABG, at our hospital from September 2013 to December 2019. Patients were divided into two groups according to the time of onset of anginal pain after CABG. Forty-five patients (58.16 ± 8.78 years) had recurrent angina in the first postoperative year after CABG and were specified as group I (early recurrence). Group II (late recurrence) comprised 82 patients (58.05 ± 8.95 years) with angina after the first year of CABG.

RESULTS

The mean preoperative left ventricular ejection fraction was 53.22 ± 8.87% in group I, and 54.7 ± 8.58% in group II (P=0.38). No significant difference was registered between groups I and II regarding preoperative angiographic findings (P>0.05). Failed grafts were found in 27.7% (n=28/101) of the grafts in group I as compared to 26.8% (n=51/190) in group II (P>0.05). Twenty-four (53.3%) patients were treated medically in group I, compared with 54 (65.8%) patients in group II (P=0.098). There was a need for intervention in 46.6% (n=21) of group I patients, and in 34.1% (n=28) of group II patients.

CONCLUSION

Recurrent angina is a complaint that should not be neglected because most of the patients with recurrent angina are diagnosed with either native coronary or graft pathology in coronary angiography performed.

Relationship between uric acid to albumin ratio and saphenous vein graft disease in patients with coronary artery bypass graft

OBJECTIVE

Saphenous vein graft disease (SVGD) remains a challenging issue for patients with coronary artery bypass grafting (CABG). It is associated with poor outcomes and atherosclerosis is the major cause of SVGD. Uric acid to albumin ratio (UAR) is a new marker which associated with cardiovascular mortality. We aim to evaluate the relationship between the SVGD and UAR.

METHODS

We retrospectively enrolled 237 patients who underwent elective coronary angiography (CAG) for stable angina or positive stress test results >1 year after CABG. The patients were divided into two groups; SVGD (+) patients and SVGD (-) patients. The SVGD was defined as presence of at least 50% stenosis in at least 1 SVG.

RESULTS

UAR were significantly higher in the SVGD (+) group (P < 0.001). Similarly, Hs-CRP, white blood cell count, and neutrophil count were significantly higher in SVGD (+) group (P = 0.03, P = 0.027 P = 0.01, respectively). In multivariate logistic regression analysis, time interval after CABG [OR = 1.161, 95% confidence interval (CI) 1.078-1.250; P < 0.001] and UAR (OR = 2.691, 95% CI 1.121-6.459; P < 0.001) were found to be independent predictors of SVGD.

CONCLUSION

Our results suggested that UAR could be a simple and available marker to predict SVGD in patients with CABG who underwent elective percutaneous coronary intervention.

Personalized coronary and myocardial blood flow models incorporating CT perfusion imaging and synthetic vascular trees

Computational simulations of coronary artery blood flow, using anatomical models based on clinical imaging, are an emerging non-invasive tool for personalized treatment planning. However, current simulations contend with two related challenges - incomplete anatomies in image-based models due to the exclusion of arteries smaller than the imaging resolution, and the lack of personalized flow distributions informed by patient-specific imaging. We introduce a data-enabled, personalized and multi-scale flow simulation framework spanning large coronary arteries to myocardial microvasculature. It includes image-based coronary anatomies combined with synthetic vasculature for arteries below the imaging resolution, myocardial blood flow simulated using Darcy models, and systemic circulation represented as lumped-parameter networks. We propose an optimization-based method to personalize multiscale coronary flow simulations by assimilating clinical CT myocardial perfusion imaging and cardiac function measurements to yield patient-specific flow distributions and model parameters. Using this proof-of-concept study on a cohort of six patients, we reveal substantial differences in flow distributions and clinical diagnosis metrics between the proposed personalized framework and empirical methods based purely on anatomy; these errors cannot be predicted a priori. This suggests virtual treatment planning tools would benefit from increased personalization informed by emerging imaging methods.

Antithrombotic strategies for preventing graft failure in coronary artery bypass graft

Coronary artery bypass graft (CABG) procedures face challenges related to graft failure, driven by factors such as acute thrombosis, neointimal hyperplasia, and atherosclerotic plaque formation. Despite extensive efforts over four decades, the optimal antithrombotic strategy to prevent graft occlusion while minimizing bleeding risks remains uncertain, relying heavily on expert opinions rather than definitive guidelines. To address this uncertainty, we conducted a review of randomized clinical trials and meta-analyses of antithrombotic therapy for patients with CABG. These studies examined various antithrombotic regimens in CABG such as single antiplatelet therapy (aspirin or P2Y12 inhibitors), dual antiplatelet therapy, and anticoagulation therapy. We evaluated outcomes including the patency of grafts, major adverse cardiovascular events, and bleeding complications and also explored future perspectives to enhance long-term outcomes for CABG patients. Early studies established aspirin as a key component of antithrombotic pharmacotherapy after CABG. Subsequent randomized controlled trials focused on adding a P2Y12 inhibitor (such as clopidogrel, ticagrelor, or prasugrel) to aspirin, yielding mixed results. This article aims to inform clinical decision-making and guide the selection of antithrombotic strategies after CABG.

The effects of glycosylation modifications on monocyte recruitment and foam cell formation in atherosclerosis

The monocyte recruitment and foam cell formation have been intensively investigated in atherosclerosis. Nevertheless, as the study progressed, it was obvious that crucial molecules participated in the monocyte recruitment and the membrane proteins in macrophages exhibited substantial glycosylation modifications. These modifications can exert a significant influence on protein functions and may even impact the overall progression of diseases. This article provides a review of the effects of glycosylation modifications on monocyte recruitment and foam cell formation. By elaborating on these effects, we aim to understand the underlying mechanisms of atherogenesis further and to provide new insights into the future treatment of atherosclerosis.

Consensus statement-graft treatment in cardiovascular bypass graft surgery

Coronary artery bypass grafting (CABG) is and continues to be the preferred revascularization strategy in patients with multivessel disease. Graft selection has been shown to influence the outcomes following CABG. During the last almost 60 years saphenous vein grafts (SVG) together with the internal mammary artery have become the standard of care for patients undergoing CABG surgery. While there is little doubt about the benefits, the patency rates are constantly under debate. Despite its acknowledged limitations in terms of long-term patency due to intimal hyperplasia, the saphenous vein is still the most often used graft. Although reendothelialization occurs early postoperatively, the process of intimal hyperplasia remains irreversible. This is due in part to the persistence of high shear forces, the chronic localized inflammatory response, and the partial dysfunctionality of the regenerated endothelium. "No-Touch" harvesting techniques, specific storage solutions, pressure controlled graft flushing and external stenting are important and established methods aiming to overcome the process of intimal hyperplasia at different time levels. Still despite the known evidence these methods are not standard everywhere. The use of arterial grafts is another strategy to address the inferior SVG patency rates and to perform CABG with total arterial revascularization. Composite grafting, pharmacological agents as well as latest minimal invasive techniques aim in the same direction. To give guide and set standards all graft related topics for CABG are presented in this expert opinion document on graft treatment.

Impact of Graft Velocity on Saphenous Vein Graft Atherosclerosis after Coronary Artery Bypass Grafting

PURPOSE

Saphenous vein grafts (SVGs) sometimes occur as vein graft stenosis or failure in coronary artery bypass grafting. The purpose of this study was to detect the factors affecting vein graft atherosclerosis.

METHODS

We performed two analysis. In the first analysis, we enrolled 120 grafts using conventionally harvested saphenous vein graft (C-SVG) and followed-up with multiple coronary computed tomography angiography (CCTA). We examined the factors that contribute to the graft atherosclerosis defined by graft failure at subsequent CCTA or substantial progression of graft stenosis (a decrease of ≥0.6 mm in diameter). In the second analysis, 66 grafts using no-touch harvested saphenous vein graft (N-SVG) were compared with those in the first analysis using C-SVG, focusing on the differences in intraoperative factors using propensity score-matched analysis.

RESULTS

In the first analysis, graft atherosclerosis+ group comprised 27 grafts, which had a larger SVG diameter, lower graft velocity, and higher graft/native ratio in diameter than the graft atherosclerosis- group. In the multivariable analysis, slow graft velocity and graft/native ≥2 in diameter were independently associated with the graft atherosclerosis. In the second analysis, the N-SVG group had a much greater graft velocity than the C-SVG group.

CONCLUSION

Lower graft velocity and higher graft/native ratio in diameter were associated with the graft atherosclerosis. The N-SVG group had increased graft velocity, which may contribute to prevent the graft atherosclerosis.(Trial registration: UMIN Clinical Trial Registry no. UMIN000050482. Registered 3 March 2023, retrospectively registered.).

Techniques and Technologies to Improve Vein Graft Patency in Coronary Surgery

Vein grafts are the most used conduits in coronary artery bypass grafting (CABG), even though many studies have suggested their lower patency compared to arterial alternatives. We have reviewed the techniques and technologies that have been investigated over the years with the aim of improving the quality of these conduits. We found that preoperative and postoperative optimal medical therapy and no-touch harvesting techniques have the strongest evidence for optimizing vein graft patency. On the other hand, the use of venous external support, endoscopic harvesting, vein preservation solution and anastomosis, and graft configuration need further investigation. We have also analyzed strategies to treat vein graft failure: when feasible, re-doing the CABG and native vessel primary coronary intervention (PCI) are the best options, followed by percutaneous procedures targeting the failed grafts.

Survival Benefit of Multiple Arterial Revascularization With and Without Supplementary Saphenous Vein Graft

Background It is unknown if the presence of saphenous vein grafting (SVG) adversely affects late survival following coronary surgery with multiple arterial grafting (MAG) versus single arterial grafting. Methods and Results A retrospective, observational, multicenter cohort study from 2001 to 2020 was conducted using the Australian and New Zealand Society of Cardiac and Thoracic Surgeons Database linked to the National Death Index. Patients undergoing primary isolated coronary artery bypass grafting with ≥2 grafts were included, and exclusions were patients aged <18 years, reoperations, concomitant or previous cardiac surgery, and the absence of arterial grafting. Demographics, comorbidities, medication, and operative configurations were propensity score matched between cohorts. The primary outcome was all-cause late death. Of 59 689 eligible patients, 35 113 were MAG (58.8%), and 24 576 were single arterial grafting (41.2%). Of the MAG cohort, 17 055 (48.6%) patients did not receive supplementary SVG (total arterial revascularization). Matching separately generated 22 764 patient pairs for MAG versus single arterial grafting, and 11 137 patient pairs for MAG with total arterial revascularization versus MAG with ≥1 supplementary vein grafts. At a median follow-up duration of 5.0 years postoperatively, the mortality rate was significantly lower for MAG than single arterial grafting (hazard ratio [HR], 0.79 [95% CI, 0.76-0.83]; P<0.001). The stratified MAG analysis found that MAG with total arterial revascularization had a lower risk of late death (HR, 0.85 [95% CI, 0.80-0.91]; P<0.001) compared with MAG with ≥1 supplementary vein grafts. Sensitivity analyses produced consistent outcomes as the primary analysis. Following adjustment for the presence of SVG in the Cox model, the survival advantage of incremental number of arteries was lost. Conclusions Multiple arterial grafting has significantly improved long-term survival compared with single arterial grafting. A further incremental survival benefit exists when no SVG is used.

Internal thoracic artery graft failure and recurrence of symptoms following single-vessel coronary artery bypass graft surgery

OBJECTIVES

Coronary events and disease recurrence following coronary artery bypass (CABG) surgery could derive from either failure in the internal thoracic artery (ITA) graft, failure in other conduits or progressive disease in the coronaries. We aim to estimate the contribution of ITA graft failure to the recurrence of symptoms after CABG surgery.

METHODS

Within the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry, we identified patients who had coronary artery bypass grafting from 1997 to 2020 with a single-vessel ITA graft bypass. Deaths, postoperative incidence of coronary angiography and the presence of a failed graft at the time of the angiography were recorded.

RESULTS

The study population consisted of 1939 patients with a mean follow-up time (SD) of 17.2 (5.6) years. The cumulative incidence (95% CI) at 20 years for a first clinically-driven postoperative angiography was 38.6% (36.2-41.1). A failed ITA graft was reported in 16.4% of the angiographies.

CONCLUSIONS

A substantial part of recurrent symptoms of coronary artery disease do not seem to be related to ITA failure. Disease progression in the native coronary vessels may instead be the main driver of symptom recurrence.

Apolipoprotein A-I vascular gene therapy reduces vein-graft atherosclerosis

Coronary artery venous bypass grafts typically fail because of atherosclerosis driven by lipid and macrophage accumulation. Therapy for vein-graft atherosclerosis is limited to statin drugs, which are only modestly effective. We hypothesized that transduction of vein-graft endothelium of fat-fed rabbits with a helper-dependent adenovirus expressing apolipoprotein AI (HDAdApoAI) would reduce lipid and macrophage accumulation. Fat-fed rabbits received bilateral external jugular vein-to-carotid artery interposition grafts. Four weeks later, one graft per rabbit (n = 23 rabbits) was infused with HDAdApoAI and the contralateral graft with HDAdNull. Grafts were harvested 12 weeks later. Paired analyses of grafts were performed, with vein graft cholesterol, intimal lipid, and macrophage content as the primary endpoints. HDAd genomes were detected in all grafts. APOAI mRNA was median 63-fold higher in HDAdApoAI grafts versus HDAdNull grafts (p < 0.001). HDAdApoAI grafts had a mean 15% lower total cholesterol (by mass spectrometry; p = 0.003); mean 19% lower intimal lipid (by oil red O staining; p = 0.02); and mean 13% lower expression of the macrophage marker CD68 (by reverse transcriptase-mediated quantitative PCR; p = 0.008). In vivo transduction of vein-graft endothelium achieves persistent APOAI expression and reduces vein-graft cholesterol, intimal lipid, and CD68 expression. Vascular gene therapy with APOAI has promise for preventing vein-graft failure caused by atherosclerosis.

Biological Materials for Tissue-Engineered Vascular Grafts: Overview of Recent Advancements

The clinical demand for tissue-engineered vascular grafts is still rising, and there are many challenges that need to be overcome, in particular, to obtain functional small-diameter grafts. The many advances made in cell culture, biomaterials, manufacturing techniques, and tissue engineering methods have led to various promising solutions for vascular graft production, with available options able to recapitulate both biological and mechanical properties of native blood vessels. Due to the rising interest in materials with bioactive potentials, materials from natural sources have also recently gained more attention for vascular tissue engineering, and new strategies have been developed to solve the disadvantages related to their use. In this review, the progress made in tissue-engineered vascular graft production is discussed. We highlight, in particular, the use of natural materials as scaffolds for vascular tissue engineering.

Personalized coronary and myocardial blood flow models incorporating CT perfusion imaging and synthetic vascular trees

Computational simulations of coronary artery blood flow, using anatomical models based on clinical imaging, are an emerging non-invasive tool for personalized treatment planning. However, current simulations contend with two related challenges - incomplete anatomies in image-based models due to the exclusion of arteries smaller than the imaging resolution, and the lack of personalized flow distributions informed by patient-specific imaging. We introduce a data-enabled, personalized and multi-scale flow simulation framework spanning large coronary arteries to myocardial microvasculature. It includes image-based coronary models combined with synthetic vasculature for arteries below the imaging resolution, myocardial blood flow simulated using Darcy models, and systemic circulation represented as lumped-parameter networks. Personalized flow distributions and model parameters are informed by clinical CT myocardial perfusion imaging and cardiac function using surrogate-based optimization. We reveal substantial differences in flow distributions and clinical diagnosis metrics between the proposed personalized framework and empirical methods based on anatomy; these errors cannot be predicted a priori. This suggests virtual treatment planning tools would benefit from increased personalization informed by emerging imaging methods.

Pathophysiology and management of saphenous vein graft disease

INTRODUCTION

The saphenous vein graft (SVG) is the most used conduit in CABG. With standardization of its use as a conduit came an understanding of its accelerated atherosclerosis, known as saphenous vein graft disease (SVGD). Given its extensive use, a review of the pathophysiology and management of SVGD is important as we optimize its use.

AREAS COVERED

For this review, an extensive literature search was completed to identify and examine the evolution of SVG in CABG, mechanisms driving SVGD, and methods developed to prevent and manage it. This includes a review of relevant major papers and trials in this space.

EXPERT OPINION

Eras of evolution in SVG usage in CABG include an experimental era, era of SVG dominance in CABG, and the current era of mixed venous and arterial grafting. As SVGD was studied, the mechanisms behind it became more understood, and prevention and management methods were developed. As advances in surgical techniques and pharmacotherapy continue to reduce occurrence and severity of SVGD, long-term patency of SV grafts continues to improve and remain excellent in optimized settings. With continued innovation and improvement in operative techniques, the SVG conduit is and will remain an important player in the field of coronary bypass.

A review on the treatment of intimal hyperplasia with perivascular medical devices: role of mechanical factors and drug release kinetics

INTRODUCTION

Intimal hyperplasia (IH) is a significant factor limiting the success of revascularization surgery for blood flow restoration. IH results from a foreign body response and mechanical disparity that involves complex biochemical reactions resulting in graft failure. The available treatment option utilizes either different pharmacological interventions or mechanical support to the vascular grafts with limited success.

AREAS COVERED

This review explains the pathophysiology of IH, responsible mechanical and biological factors, and treatment options, emphasizing perivascular devices. They are designed to provide mechanical support and pharmacology actions. The perivascular drug delivery concept has successfully demonstrated efficacy in various animal studies. Accurate projections of drug release mechanisms using mathematical modeling could be used to formulate prolonged drug elution devices. Numerical modeling aspects for the prediction of design outcomes have been given due importance that fulfills the unmet clinical need for better patient care.

EXPERT OPINION

IH could be effectively prevented by simultaneous mechanical scaffolding and sustained local drug delivery. Future perivascular medical devices could be designed to integrate these essential features. Numerical modeling for device performance prediction should be utilized in the development of next-generation perivascular devices.

Perivascular patch using biodegradable polymers: Investigation of mechanical and drug elution characteristics

Intimal hyperplasia (IH) is the primary cause for the vascular graft stenosis. Perivascular devices offer a potential treatment option to reduce the impact of intimal hyperplasia by providing mechanical support and local administration of therapeutic agents to control cellular overgrowth. In the present study, a perivascular patch primarily made up of biodegradable polymer, Poly L-Lactide, has been designed with adequate mechanical strength and ability for sustained drug elution of anti-proliferative drug (Paclitaxel). The elastic modulus of the polymeric film has been optimized by blending the base polymer with different grades of biocompatible polyethylene glycols. Using design of experiments, the optimized parameters were obtained as PLLA with 2.5% PEG-6000 and have shown 3.14 MPa elastic modulus. The film prepared based on optimum conditions has been employed for prolonged drug delivery (about four months) under simulated physiological conditions. The addition of drug release rate enhancer (polyvinyl pyrrolidone K90F) has improved the drug elution rate and ∼83% drug was released over entire study period. The molecular weight of the base biodegradable polymer was estimated by gel permeation chromatography (GPC) which remained unchanged during the drug release study duration. Evidences of Paclitaxel drug crystallization were found to contribute to the sustained drug elution. The SEM examination of the surface morphology post-incubation revealed micropores on the surface, contributing to the overall drug release rate. The study concluded that perivascular biodegradable films could be tailored for their mechanical properties, and sustained drug elution could also be formulated with reasonable choices of biodegradable polymer and biocompatible additives.

Fate mapping RNA-sequencing reveal Malat1 regulates Sca1+ progenitor cells to vascular smooth muscle cells transition in vascular remodeling

Regeneration of smooth muscle cells (SMCs) is vital in vascular remodeling. Sca1⁺ stem/progenitor cells (SPCs) can generate de novo smooth muscle cells after severe vascular injury during vessel repair and regeneration. However, the underlying mechanisms have not been conclusively determined. Here, we reported that lncRNA Metastasis-associated lung adenocarcinoma transcript 1 (Malat1) was down-regulated in various vascular diseases including arteriovenous fistula, artery injury and atherosclerosis. Using genetic lineage tracing mice and veingraft mice surgery model, we found that suppression of lncRNA Malat1 promoted Sca1⁺ cells to differentiate into SMCs in vivo, resulting in excess SMC accumulation in neointima and vessel stenosis. Genetic ablation of Sca1⁺ cells attenuated venous arterialization and impaired vascular structure normalization, and thus, resulting in less Malat1 down-regulation. Single cell sequencing further revealed a fibroblast-like phenotype of Sca1⁺ SPCs-derived SMCs. Protein array sequencing and in vitro assays revealed that SMC regeneration from Sca1⁺ SPCs was regulated by Malat1 through miR125a-5p/Stat3 signaling pathway. These findings delineate the critical role of Sca1⁺ SPCs in vascular remodeling and reveal that lncRNA Malat1 is a key regulator and might serve as a novel biomarker or potential therapeutic target for vascular diseases.

Symptomatic late saphenous vein graft failure in coronary artery bypass surgery

OBJECTIVES

Coronary artery bypass grafting for advanced coronary artery disease is a well-established procedure with excellent long-term results. The issue of saphenous vein graft (SVG) performance and its relation to clinical symptoms and thereby the potential for improvement by using superior grafts are still not fully understood. We aim to estimate the contribution of late SVG failure to the long-term outcome.

METHODS

A study population operated between 1997 and 2020, with an internal thoracic artery with a single distal anastomosis and 1, 2 or 3 distal SVG anastomoses, was isolated from the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry. Data regarding postoperative clinically driven coronary angiography and status of bypass grafts were collected.

RESULTS

The study population consisted of 44 951 patients. Clinically driven angiography occurred in 10.1% (9.5-10.8), 7.9% (7.6-8.3) and 7.1% (6.7-7.5), respectively, of patients within 3 years and 23.6% (22.6-24.5), 20.0% (19.5-20.6) and 17.5% (16.9-18.2), respectively, of patients within 10 years after surgery. Excluding the first 3 postoperative years, no failed SVGs were found in >75%, 60% and 45%, respectively, of cases when an angiography was performed in the first 10 years after surgery.

CONCLUSIONS

The results suggest that the risk of symptomatic graft failure due to vein graft disease during the first 10 years after surgery is in the range of 1-2% for every grafted coronary vessel and provide an estimate for the upper limit of the improvements in results that could be achieved by replacing SVGs with superior grafts.

Venous External Support in Coronary Artery Bypass Surgery: A Systematic Review and Meta-Analysis

OBJECTIVES

Neointimal hyperplasia and lumen irregularities are major contributors to vein graft failure and the use of VEST^(R) should prevent this. In this review, we aim to evaluate the angiographic outcomes of externally supported vein grafts.

METHODS

Medline, Embase and Cochrane Library were systematically reviewed for randomized clinical trials published by August 2022. The primary outcome was graft failure. Secondary outcomes included graft ectasia, intimal hyperplasia area and thickness, and graft non-uniformity. Odds ratios (OR) for dichotomous variables and mean difference (MD) for continuous variables with 95% confidence intervals (CI) were pooled using a fixed-effects model.

RESULTS

Three randomized controlled trials with a total of 437 patients were included with follow-up ranging from 1 to 2 years. The odds of graft failure were similar in the two groups (OR 1.22; 95%CI 0.88 to 1.71; I²=0%). Intimal hyperplasia area [MD -0.77 mm²; 95%CI -1.10 to -0.45; I²=0%] and thickness [MD -0.06 mm; 95%CI -0.08 to -0.04; I²=0%] were significantly lower in the VEST group. Fitzgibbon Patency Scale of II or III (representing angiographic conduit non-uniformity; OR 0.67; 95%CI 0.48 to 0.94; I²=0%) and graft ectasia (OR 0.53; 95%CI 0.32 to 0.88; I²=33%) were also significantly lower in the VEST group.

CONCLUSIONS

At short-term follow-up, VEST does not seem to reduce the incidence of graft failure, although it is associated with attenuation of intimal hyperplasia and non-uniformity. Longer angiographic follow-up is warranted to determine whether these positive effects might translate into a positive effect in graft failure and in long-term clinical outcomes.

Graft thrombosis after coronary artery bypass surgery and current practice for prevention

Coronary artery bypass grafting (CABG) is the most frequently performed cardiac surgery worldwide. The reported incidence of graft failure ranges between 10% and 50%, depending upon the type of conduit used. Thrombosis is the predominant mechanism of early graft failure, occurring in both arterial and vein grafts. Significant advances have been made in the field of antithrombotic therapy since the introduction of aspirin, which is regarded as the cornerstone of antithrombotic therapy for prevention of graft thrombosis. Convincing evidence now exists that dual antiplatelet therapy (DAPT), consisting of aspirin and a potent oral P2Y12 inhibitor, effectively reduces the incidence of graft failure. However, this is achieved at the expense of an increase in clinically important bleeding, underscoring the importance of balancing thrombotic risk and bleeding risk when considering antithrombotic therapy after CABG. In contrast, anticoagulant therapy has proved ineffective at reducing the occurrence of graft thrombosis, pointing to platelet aggregation as the key driver of graft thrombosis. We provide a comprehensive review of current practice for prevention of graft thrombosis and discuss potential future concepts for antithrombotic therapy including P2Y12 inhibitor monotherapy and short-term DAPT.

Beyond CFD: Emerging methodologies for predictive simulation in cardiovascular health and disease

Physics-based computational models of the cardiovascular system are increasingly used to simulate hemodynamics, tissue mechanics, and physiology in evolving healthy and diseased states. While predictive models using computational fluid dynamics (CFD) originated primarily for use in surgical planning, their application now extends well beyond this purpose. In this review, we describe an increasingly wide range of modeling applications aimed at uncovering fundamental mechanisms of disease progression and development, performing model-guided design, and generating testable hypotheses to drive targeted experiments. Increasingly, models are incorporating multiple physical processes spanning a wide range of time and length scales in the heart and vasculature. With these expanded capabilities, clinical adoption of patient-specific modeling in congenital and acquired cardiovascular disease is also increasing, impacting clinical care and treatment decisions in complex congenital heart disease, coronary artery disease, vascular surgery, pulmonary artery disease, and medical device design. In support of these efforts, we discuss recent advances in modeling methodology, which are most impactful when driven by clinical needs. We describe pivotal recent developments in image processing, fluid-structure interaction, modeling under uncertainty, and reduced order modeling to enable simulations in clinically relevant timeframes. In all these areas, we argue that traditional CFD alone is insufficient to tackle increasingly complex clinical and biological problems across scales and systems. Rather, CFD should be coupled with appropriate multiscale biological, physical, and physiological models needed to produce comprehensive, impactful models of mechanobiological systems and complex clinical scenarios. With this perspective, we finally outline open problems and future challenges in the field.

Protein O-GlcNAcylation in cardiovascular diseases

O-GlcNAcylation is a post-translational modification of protein in response to genetic variations or environmental factors, which is controlled by two highly conserved enzymes, i.e. O-GlcNAc transferase (OGT) and protein O-GlcNAcase (OGA). Protein O-GlcNAcylation mainly occurs in the cytoplasm, nucleus, and mitochondrion, and it is ubiquitously implicated in the development of cardiovascular disease (CVD). Alterations of O-GlcNAcylation could cause massive metabolic imbalance and affect cardiovascular function, but the role of O-GlcNAcylation in CVD remains controversial. That is, acutely increased O-GlcNAcylation is an adaptive heart response, which temporarily protects cardiac function. While it is harmful to cardiomyocytes if O-GlcNAcylation levels remain high in chronic conditions or in the long run. The underlying mechanisms include regulation of transcription, energy metabolism, and other signal transduction reactions induced by O-GlcNAcylation. In this review, we will focus on the interactions between protein O-GlcNAcylation and CVD, and discuss the potential molecular mechanisms that may be able to pave a new avenue for the treatment of cardiovascular events.

Left Internal Mammary Artery as an Endocrine Organ: Insights Into Graft Biology and Long-term Impact Following Coronary Artery Bypass Grafting

The left internal mammary artery (LIMA) is considered the criterion standard vessel for use in coronary artery bypass grafting. In recent decades, countless studies have documented its superiority over other arterial and venous coronary artery bypass grafting conduits, although the full mechanisms for this superiority remain unknown. A growing body of literature has unveiled the importance of extracellular vesicles known as exosomes in cardiovascular signaling and various pathologic states. In this review, we briefly compare the clinical longevity of the LIMA relative to other conduits, explore the effects of varying grafting techniques on clinical and angiographic outcomes, and provide physiologic insights into graft function on a cellular and molecular level. Finally, we explore exosome signaling as it pertains to atherosclerosis in support of the LIMA as an "endocrine organ."

Doppler Ultrasound Selection and Follow-Up of the Internal Mammary Artery as Coronary Graft

The impact of coronary artery disease (CAD) on all-cause mortality and overall disabilities is well-established. Percutaneous and/or surgical coronary revascularization procedures dramatically reduced the occurrence of adverse cardiovascular events in patients suffering from atherosclerosis. Specifically, guidelines from the European Society of Cardiology on the management of myocardial revascularization promoted coronary artery by-pass graft (CABG) intervention in patients with specific alterations in the coronary tree due to the higher beneficial effects of this procedure as compared to the percutaneous one. The left internal mammary artery (LIMA) is one of the best-performing vessels in CABG procedures due to its location and its own structural characteristics. Nevertheless, the non-invasive assessment of its patency is challenging. Doppler ultrasonography (DU) might perform as a reliable technique for the non-invasive evaluation of the patency of LIMA. Data from the literature revealed that DU may detect severe (>70%) stenosis of the LIMA graft. In this case, pulsed-wave Doppler might show peak diastolic velocity/peak systolic velocity < 0.5 and diastolic fraction < 50%. A stress test might also be adopted for the evaluation of patency of LIMA through DU. The aim of this narrative review is to evaluate the impact of DU on the evaluation of the patency of LIMA graft in patients who undergo follow-up after CABG intervention.

Systemic Delivery of Clopidogrel Inhibits Neointimal Formation in a Mouse Vein Graft Model

ABSTRACT

Clopidogrel inhibits platelet aggregation and has beneficial effects on patients undergoing coronary artery bypass grafting surgery, but it is unknown whether clopidogrel inhibits the neointima formation of grafted veins. In this study, we used a murine vein graft model to study the effect of clopidogrel on intima hyperplasia of the vein graft. Vein grafting was performed among C57BL/6J mice, immediately after surgery; 1 mg/kg clopidogrel and vehicle control were used to inject mice peritoneally daily for 2 weeks. As compared with the vehicle, clopidogrel significantly inhibited the neointima formation of vein grafts at 4 weeks after surgeries. The immunohistochemistry study showed that as compared with the vehicle, clopidogrel significantly decreased the rate of proliferating cell nuclear antigen-positive cells in the wall of vein grafts and significantly increased the expression of vascular smooth muscle cell (VSMC) contractile protein markers (α-smooth muscle actin, calponin, and SM22) within the neointima area of vein grafts. Clopidogrel significantly decreased the plasma interleukin 6 (IL-6) level at 1 week after surgery as compared with the vehicle. We isolated VSMCs from mouse aortic arteries. As compared with the vehicle, clopidogrel significantly inhibited thrombin-induced VSMC proliferation and migration, significantly decreased IL-6 mRNA expression and protein secretion, and increased intracellular cyclic adenosine monophosphate generation in a dose-dependent manner. In conclusion, systemic delivery of clopidogrel inhibits neointima formation of the mouse vein graft, the mechanisms of which are associated with its inhibitory effects on VSMC proliferation, migration, and the tendency to synthetic phenotype after vein graft surgery, reducing the expression of IL-6 and increasing the intracellular cyclic adenosine monophosphate level.

Defective autophagy triggered by arterial cyclic stretch promotes neointimal hyperplasia in vein grafts via the p62/nrf2/slc7a11 signaling pathway

Autophagy is an adaptation mechanism to keep cellular homeostasis, and its deregulation is implicated in various cardiovascular diseases. After vein grafting, hemodynamic factors play crucial roles in neointimal hyperplasia, but the mechanisms are poorly understood. Here, we investigated the impacts of arterial cyclic stretch on autophagy of venous smooth muscle cells (SMCs) and its role in neointima formation after vein grafting. Rat jugular vein graft were generated via the 'cuff' technique. Autophagic flux in venous SMCs is impaired in 3-day, 1-week and 2-week grafted veins. 10%-1.25 Hz cyclic stretch (arterial stretch) loaded with FX5000 stretch system on venous SMCs blocks cellular autophagic flux in vitro and shows no significant impact on activity of mTORC1 and AMPK. Microtubule depolymerization but not lysosome dysfunction nor autophagosome/amphisome-lysosomal membrane fusion blockade is involved in the impairment of autophagic flux. Microtubule stabilization, induced by paclitaxel treatment and external stents intervention respectively, restores venous SMC autophagy and ameliorates neointimal hyperplasia in vivo. Moreover, autophagy impairment causes accumulation of the cargo receptor p62, which sequesters keap1 to p62 aggregates and results in the stabilization and nuclear translocation of nrf2 to modulate its target antioxidative gene SLC7A11. p62 silencing abrogates the increases of nrf2 and slc7a11 protein expression, glutathione level and venous SMC proliferation triggered by arterial cyclic stretch in vitro, and further hinders nrf2 nuclear translocation, reduces neointimal thickness after vein grafting in vivo. p62 (T349A) mutation also inhibited venous SMC proliferation and alleviated neointimal formation in vivo. These findings suggest that stabilization of microtubules to rescue autophagic flux or direct silencing of p62 are potential therapeutic strategies for neointimal hyperplasia.

Cerium dioxide nanoparticles modulate antioxidant defences and change vascular response in the human saphenous vein

Nanoparticles have a promising future in biomedical applications and knowing whether they affect ex vivo vascular reactivity is a necessary step before their use in patients. In this study, we have evaluated the vascular effect of cerium dioxide nanoparticles (CeO₂NPs) on the human saphenous vein in response to relaxing and contractile agonists. In addition, we have measured the protein expression of key enzymes related to vascular homeostasis and oxidative stress. We found that CeO₂NPs increased expression of both SOD isoforms, and the consequent reduction of superoxide anion would enhance the bioavailability of NO explaining the increased vascular sensitivity to sodium nitroprusside in the presence of CeO₂NPs. The NOX4 reduction induced by CeO₂NPs may lead to lower H₂O₂ synthesis associated with vasodilation through potassium channels explaining the lower vasodilation to bradykinin. In addition, we showed for the first time, that CeO₂NPs increase the expression of ACE2 in human saphenous vein, and it may be the cause of the reduced contraction to angiotensin II. Moreover, we ruled out that CeO₂NPs have effect on the protein expression of eNOS, sGC, BKca channels and angiotensin II receptors or modify the vascular response to noradrenaline, endothelin-1 and TXA₂ analogue. In conclusion, CeO₂NPs show antioxidant properties, and together with their vascular effect, they could be postulated as adjuvants for the treatment of cardiovascular diseases.

Microfluidic bioprinting of tough hydrogel-based vascular conduits for functional blood vessels

Three-dimensional (3D) bioprinting of vascular tissues that are mechanically and functionally comparable to their native counterparts is an unmet challenge. Here, we developed a tough double-network hydrogel (bio)ink for microfluidic (bio)printing of mono- and dual-layered hollow conduits to recreate vein- and artery-like tissues, respectively. The tough hydrogel consisted of energy-dissipative ionically cross-linked alginate and elastic enzyme-cross-linked gelatin. The 3D bioprinted venous and arterial conduits exhibited key functionalities of respective vessels including relevant mechanical properties, perfusability, barrier performance, expressions of specific markers, and susceptibility to severe acute respiratory syndrome coronavirus 2 pseudo-viral infection. Notably, the arterial conduits revealed physiological vasoconstriction and vasodilatation responses. We further explored the feasibility of these conduits for vascular anastomosis. Together, our study presents biofabrication of mechanically and functionally relevant vascular conduits, showcasing their potentials as vascular models for disease studies in vitro and as grafts for vascular surgeries in vivo, possibly serving broad biomedical applications in the future.

Current intraoperative storage and handling practices of autologous bypass conduit: A survey of the royal australasian college of surgeons

During bypass surgery for peripheral arterial occlusive disease and ischaemic heart disease, autologous graft conduit including great saphenous veins and radial arteries are frequently stored in solution. Endothelial damage adversely affects the performance and patency of autologous bypass grafts, and intraoperative graft storage solutions have been shown to influence this process. The distribution of storage solutions currently used amongst Cardiothoracic and Vascular Surgeons from Australia and New Zealand is not well defined in the literature. The aim of this study was to determine current practices regarding autologous graft storage and handling amongst this cohort of surgeons, and discuss their potential relevance in the context of early graft failure. From this survey, the most frequently used storage solutions were heparinized saline for great saphenous veins, and pH-buffered solutions for radial arteries. Duration of storage was 30–45 min for almost half of respondents, although responses to this question were limited. Further research is required to investigate whether ischaemic endothelial injury generates a prothrombotic state, whether different storage media can alter this state, and whether this is directly associated with clinical outcomes of interest such as early graft failure.

Diagnostic and Management Strategies in Patients with Late Recurrent Angina after Coronary Artery Bypass Grafting

Purpose of Review

This review will outline the current evidence on the anatomical, functional, and physiological tools that may be applied in the evaluation of patients with late recurrent angina after coronary artery bypass grafting (CABG). Furthermore, we discuss management strategies and propose an algorithm to guide decision-making for this complex patient population.

Recent Findings

Patients with prior CABG often present with late recurrent angina as a result of bypass graft failure and progression of native coronary artery disease (CAD). These patients are generally older, have a higher prevalence of comorbidities, and more complex atherosclerotic lesion morphology compared to CABG-naïve patients. In addition, guideline recommendations are based on studies in which post-CABG patients have been largely excluded.

Summary

Several invasive and non-invasive diagnostic tools are currently available to assess graft patency, the hemodynamic significance of native CAD progression, left ventricular function, and myocardial viability. Such tools, in particular the latest generation coronary computed tomography angiography, are part of a systematic diagnostic work-up to guide optimal repeat revascularization strategy in patients presenting with late recurrent angina after CABG.

External Support for Saphenous Vein Grafts in Coronary Artery Bypass Surgery: A Randomized Clinical Trial

Importance

Intimal hyperplasia and subsequent saphenous vein graft failure may have significant adverse clinical effects in patients undergoing coronary artery bypass surgery. External support of saphenous vein grafts has the potential to prevent vein graft dilation and hence slow the rate of intimal hyperplasia and increase long-term vein patency.

Objective

To determine efficacy, as measured by intimal hyperplasia, and safety of an external saphenous vein graft support device in patients undergoing a coronary bypass graft procedure.

Design, Setting, and Participants

This within-patient randomized, open-label, multicenter study was conducted at 17 Cardiothoracic Surgical Trials Network centers in North America. Between January 2018 and February 2019, 224 patients with multivessel coronary artery disease undergoing isolated bypass surgery were enrolled. For each patient, 1 of 2 vein grafts was randomized to receive external support or no support.

Interventions

External vein graft support or no support.

Main Outcomes and Measures

The primary efficacy end point was intimal hyperplasia area assessed by intravascular ultrasound at 12 months postrandomization for each study graft. Secondary confirmatory end points were lumen diameter uniformity assessed by angiography and graft failure (≥50% stenosis) by quantitative coronary angiography. Major cardiac and cerebrovascular events were collected through month 12.

Results

Among 224 patients (mean [SD] age, 65.8 [8.3] years; 178 [79.5%] male), 203 (90.6%) were eligible for intravascular ultrasound, of which 85 (41.9%) had at least 1 study graft occluded or severely diseased at 12 months (55 supported, 56 unsupported). After imputation of data missing because of graft occlusion or severe disease, the estimated mean (SE) intimal hyperplasia area was 5.11 (0.16) mm2 in supported grafts and 5.79 (0.20) mm2 in unsupported grafts (P = .07). In a sensitivity analysis of 113 patients with both grafts imaged, the mean intimal hyperplasia area was 4.58 (0.18) mm2 and 5.12 (0.23) mm2 in supported and unsupported grafts, respectively (P = .04). By 12 months, 5 patients (2.2%) died and 16 patients (7.1%) experienced a major cardiac or cerebrovascular event.

Conclusions and Relevance

The 12-month difference in intimal hyperplasia area between supported and unsupported grafts did not achieve statistical significance. Cumulative mortality and major cardiac or cerebrovascular events rates were similar to those in other randomized coronary artery bypass trials. Further investigation to assess the effect of external graft support devices on long-term graft patency and clinical outcomes is warranted.

Trial Registration

ClinicalTrials.gov Identifier: NCT03209609.

Graft flow assessment and early coronary artery bypass graft failure: a computed tomography analysis

OBJECTIVES

We evaluated graft patency by computed tomography and explored the determinants of intraoperative mean graft flow (MGF) and its contribution to predict early graft occlusion.

METHODS

One hundred and forty-eight patients under a single surgeon were prospectively enrolled. Arterial and endoscopically harvested venous conduits were used. Intraoperative graft characteristics and flows were collected. Graft patency was blindly evaluated by a follow-up computed tomography at 11.4 weeks (median).

RESULTS

Graft occlusion rate was 5.2% (n = 22 of 422; 8% venous and 3% arterial). Thirteen were performed on non-significant proximal stenosis while 9 on occluded or >70% stenosed arteries. Arterial and venous graft MGF were lower in females (Parterial = 0.010, Pvenous = 0.009), with median differences of 10 and 13.5 ml/min, respectively. Arterial and venous MGF were associated positively with target vessel diameter ≥1.75 mm (Parterial = 0.025; Pvenous = 0.002) and negatively with pulsatility index (Parterial < 0.001; Pvenous < 0.001). MGF was an independent predictor of graft occlusion, adjusting for EuroSCORE-II, pulsatility index, graft size and graft type (arterial/venous). An MGF cut-off of 26.5 ml/min for arterial (sensitivity 83.3%, specificity 80%) and 36.5 ml/min for venous grafts (sensitivity 75%, specificity 62%) performed well in predicting early graft occlusion.

CONCLUSIONS

We demonstrate that MGF absolute values are influenced by coronary size, gender and graft type. Intraoperative MGF of >26.5 ml/min for arterial and >36.5 ml/min for venous grafts is the most reliable independent predictor of early graft patency. Modern-era coronary artery bypass graft is associated with low early graft failure rates when transit time flow measurement is used to provide effective intraoperative quality assurance.

Influence of cholesterol level on long-term survival and cardiac events after surgical coronary revascularization

Objective

Statins have been shown to delay the inevitable progression of atherosclerosis in native coronaries and saphenous vein grafts, thereby reducing ischemic events after surgical coronary revascularization. However, there is significant controversy as to whether titrating statin therapy to concrete cholesterol targets is appropriate.

Methods

A single-center retrospective analysis of 309 consecutive patients who underwent isolated coronary artery bypass graft in 2007 and 2008 was performed. Measurements of lipid profile subcomponents, namely total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides, in mmol/L, were obtained by retrospective review of electronic health records. The primary end point was cardiac death. The secondary end point was the composite of cardiac events, including cardiac death, nonfatal myocardial infarction, hospitalization for unstable angina, and target lesion revascularization. Database lock date was August 15, 2020.

Results

The median follow-up duration was 12.5 years. Cardiac death occurred in 6.8% of the cohort. Cardiac events occurred in 21.7% of the cohort. New-onset myocardial infarction occurred in 8.7% (n = 27), of which 48.1% (n = 13) underwent repeat revascularization. A 2-level nested Cox proportional hazards regression model was constructed to determine whether cholesterol target attainment was independently associated with cardiac events. After risk adjustment, LDL-C, non–HDL-C, total cholesterol (TC), and TC/HDL-C ratio were independently associated with cardiac death. In receiver operating characteristics analyses, the optimal cut-off values for non–HDL-C, LDL-C, and TC/HDL-C ratio were 3.2 mmol/L, 2.3 mmol/L, and 3.5, respectively.

Conclusions

Exposure to elevated LDL-C and non–HDL-C cholesterol levels independently predicted long-term cardiac death after coronary artery bypass graft.

Light-Activated Vascular Anastomosis

Background. There have been few advances in technique since vascular anastomosis was performed with silk suture on a curved needle in 1902. This technique results in disruption of the endothelium with exposed intraluminal suture, both of which may lead to thrombocyte aggregation, intimal hyperplasia, and vascular stenosis. A variety of alternative techniques have been explored, with limited success. Photochemical tissue bonding (PTB) is a light-activated methodology of rapidly cross-linking tissue interfaces at the molecular level. Herein, we describe a new technique for anastomosis of venous interposition graft in an ovine model of femoral artery bypass utilizing PTB. Methods. Polypay specific pathogen free sheep (n = 5; 40-45 kg) underwent femoral artery bypass utilizing saphenous vein. The femoral artery was transected and reversed saphenous vein was implanted as an interposition graft. The proximal anastomosis was created as a vein-over-artery cuff utilizing PTB, and the distal anastomosis was created with standard interrupted 8-0 polypropylene suture. Four weeks post-index operation, femoral angiogram was performed to evaluate patency, tortuosity, and luminal diameter. All bypass grafts were harvested and longitudinal and transverse histological sections from the proximal anastomosis were analyzed. Results. The PTB anastomoses (n = 5) were immediately watertight and patent. All animals survived the 28-day study duration. Angiography revealed patent grafts with no aneurysm or stenosis (n = 5). Histologic examination revealed integration of the venous endothelium with the arterial adventitia. Conclusion. Photochemical tissue bonding creates an immediate strong, watertight vascular anastomosis that can withstand physiologic arterial pressure and remains patent at 28 days without the need for intraluminal suture.

Bypass Grafting and Native Coronary Artery Disease Activity

OBJECTIVES

The aim of this study was to describe the potential of 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) to identify graft vasculopathy and to investigate the influence of coronary artery bypass graft (CABG) surgery on native coronary artery disease activity and progression.

BACKGROUND

As well as developing graft vasculopathy, CABGs have been proposed to accelerate native coronary atherosclerosis.

METHODS

Patients with established coronary artery disease underwent baseline 18F-NaF PET, coronary artery calcium scoring, coronary computed tomographic angiography, and 1-year repeat coronary artery calcium scoring. Whole-vessel coronary microcalcification activity (CMA) on 18F-NaF PET and change in calcium scores were quantified in patients with and without CABG surgery.

RESULTS

Among 293 participants (mean age 65 ± 9 years, 84% men), 48 (16%) underwent CABG surgery 2.7 years [IQR: 1.4-10.4 years] previously. Although all arterial and the majority (120 of 128 [94%]) of vein grafts showed no 18F-NaF uptake, 8 saphenous vein grafts in 7 subjects had detectable CMA. Bypassed native coronary arteries had 3 times higher CMA values (2.1 [IQR: 0.4-7.5] vs 0.6 [IQR: 0-2.7]; P < 0.001) and greater progression of 1-year calcium scores (118 Agatston unit [IQR: 48-194 Agatston unit] vs 69 [IQR: 21-142 Agatston unit]; P = 0.01) compared with patients who had not undergone CABG, an effect confined largely to native coronary plaques proximal to the graft anastomosis. In sensitivity analysis, bypassed native coronary arteries had higher CMA (2.0 [IQR: 0.4-7.5] vs 0.8 [IQR: 0.3-3.2]; P < 0.001) and faster disease progression (24% [IQR: 16%-43%] vs 8% [IQR: 0%-24%]; P = 0.002) than matched patients (n = 48) with comparable burdens of coronary artery disease and cardiovascular comorbidities in the absence of bypass grafting.

CONCLUSIONS

Native coronary arteries that have been bypassed demonstrate increased disease activity and more rapid disease progression than nonbypassed arteries, an observation that appears independent of baseline atherosclerotic plaque burden. Microcalcification activity is not a dominant feature of graft vasculopathy.

Chronic Total Occlusion Percutaneous Coronary Intervention in Patients With Prior Coronary Artery Bypass Graft: Current Evidence and Future Perspectives

Coronary chronic total occlusion (CTO), which occurs in 18. 4–52% of all patients referred for coronary angiography, represents one of the last barriers in coronary intervention. Approximately half of all patients with prior coronary artery bypass graft (CABG), who undergo coronary angiography, are diagnosed with coronary CTO. In fact, these patients often develop recurrent symptoms and events, necessitating revascularization. Currently, there is neither a consensus nor developed guidelines for the treatment of CTO patients with prior CABG, and the prognosis of these patients remains unknown. In this review, we discuss current evidence and future perspectives on CTO revascularization in patients with prior CABG, with special emphasis on clinical and lesion characteristics, procedural success rates, periprocedural complications, and long-term outcomes.

Ticagrelor versus aspirin 2 years after coronary bypass: Observational analysis from the TARGET trial

BACKGROUND

Compared to conventional aspirin therapy, ticagrelor did not improve vein graft patency 1 year after coronary bypass surgery (CABG) in the ticagrelor antiplatelet therapy to reduce graft events and thrombosis (TARGET) trial. However, it is unknown whether ticagrelor may impact graft patency long-term following surgery.

METHODS

In the TARGET multicenter trial, 250 CABG patients were randomized to aspirin 81 mg or ticagrelor 90 mg twice daily. In this observational analysis, 2 years after surgery, vein graft occlusion and clinical events were compared among subjects who agreed to a second year of double-blind study drug administration (N = 156).

RESULTS

Two-year graft assessment was performed for 142 patients (80 aspirin patients, 62 ticagrelor patients, 425 total grafts), with an overall 2-year graft occlusion rate of 10.6%. Vein graft occlusion at 2 years, the primary outcome of this study, did not significantly differ between the two groups (15.7% vs. 13.2%, aspirin vs. ticagrelor, p = .71). The incidence of vein grafts with any disease (stenosis or occlusion) did not significantly differ between the groups (19.4% vs. 19.8%, aspirin vs. ticagrelor, p = 1.00), and the number of patients with vein graft disease did not significantly differ between the groups (30.0% vs. 29.0%, aspirin vs. ticagrelor, p = 1.00). Vein grafts developing new disease did not significantly differ between the two groups (1.5% vs. 3.8%, aspirin vs. ticagrelor, p = .41). Freedom from major adverse cardiovascular events at 2 years was similar between the groups (p = .75).

CONCLUSION

Compared to conventional aspirin therapy, ticagrelor did not significantly reduce vein graft disease 2 years after CABG.

Rationale and design of a randomized trial evaluating an external support device for saphenous vein coronary grafts

BACKGROUND

Coronary artery bypass grafting (CABG) is the most common revascularization approach for the treatment of multi-vessel coronary artery disease. While the internal mammary artery is nearly universally used to bypass the left anterior descending coronary artery, autologous saphenous vein grafts (SVGs) are still the most frequently used conduits to grafts the remaining coronary artery targets. Long-term failure of these grafts, however, continues to limit the benefits of surgery.

METHODS

The Cardiothoracic Surgical Trials Network trial of the safety and effectiveness of a Venous External Support (VEST) device is a randomized, multicenter, within-patient trial comparing VEST-supported versus unsupported saphenous vein grafts in patients undergoing CABG. Key inclusion criteria are the need for CABG with a planned internal mammary artery to the left anterior descending and two or more saphenous vein grafts to other coronary arteries. The primary efficacy endpoint of the trial is SVG intimal hyperplasia (plaque + media) area assessed by intravascular ultrasound at 12 months post randomization. Occluded grafts are accounted for in the analysis of the primary endpoint. Secondary confirmatory endpoints are lumen diameter uniformity and graft failure (>50% stenosis) assessed by coronary angiography at 12 months. The safety endpoints are the occurrence of major adverse cardiac and cerebrovascular events and hospitalization within 5 years from randomization.

CONCLUSIONS

The results of the VEST trial will determine whether the VEST device can safely limit SVG intimal hyperplasia in patients undergoing CABG as treatment for coronary atherosclerotic disease.

Platelet-derived microvesicles regulate vascular smooth muscle cell energy metabolism via PRKAA after intimal injury

Vascular intimal injury initiates various cardiovascular disease processes. Exposure to subendothelial collagen can cause platelet activation, leading to platelet-derived microvesicles (aPMVs) secretion. In addition, vascular smooth muscle cells (VSMCs) exposed to large amounts of aPMVs undergo abnormal energy metabolism, they proliferate excessively and migrate after the loss of endothelium, eventually contributing to neointimal hyperplasia. However, the roles of aPMVs in VSMC energy metabolism are still unknown. Carotid artery intimal injury model indicated platelets adhered to injured blood vessels. In vitro, p-Pka content was increased in aPMVs. aPMVs significantly changed VSMC glycolysis and oxidative phosphorylation, and promoted VSMC migration and proliferation by upregulating p-PRKAA/p-FoxO1. Compound C, an inhibitor of PRKAA, effectively reversed the cell function and energy metabolism triggered by aPMVs in vitro and neointimal formation in vivo. Our data show that aPMVs can affect VSMC energy metabolism through the Pka/PRKAA/FoxO1 signaling pathway and ultimately affect VSMC function, indicating that VSMC metabolic phenotype shifted by aPMVs can be considered a potential target for the inhibition of hyperplasia and providing a new perspective for regulating the abnormal activity of VSMCs after injury.

Rivaroxaban as Therapy for Saphenous Venous Graft Failure due to Venous Outflow Mismatch

Background

Recurrent angina and long-term occlusion following coronary artery bypass graft surgery is often treated with percutaneous coronary intervention, a high-risk intervention for distal embolization. Here, we present the utilization of the novel oral anticoagulant, rivaroxaban, in the treatment of saphenous vein graft thrombosis with complete resolution of the thrombus secondary to graft outflow mismatch. Case Presentation. A 69-year-old man with triple coronary artery bypass grafting using a saphenous vein and left internal mammary artery, performed in 2017, presented at our hospital for recurrent angina. Coronary angiography revealed a patent LIMA to LAD and a large clot burden in the venous conduit to the first OM/terminal circumflex—theorized to be due to an outflow mismatch of the large saphenous vein to the native artery resulting in stasis. Instead of percutaneous coronary intervention, he was treated with rivaroxaban 20 mg once a day. The angiography 4 weeks after starting rivaroxaban showed complete resolution of the thrombus.

Conclusion

Rivaroxaban could become a potential treatment option in thrombus reversal due to static venous flow with subsequent long-term patency of the graft. Additionally, its use may be indicated in the generalized prevention of VGF.

Saphenous vein harvesting techniques for coronary artery bypass grafting: a systematic review and meta-analysis

The great saphenous vein (GSV) graft remains a frequently used conduit for coronary artery bypass graft (CABG) surgery. The optimal technique for GSV harvesting has been the subject of on-going controversy. We therefore sought to conduct a systematic review and meta-analysis of all available GSV harvesting techniques in CABG. A systematic search of 12 electronic databases was performed to identify all randomized controlled trials (RCTs) of any GSV harvesting technique, including conventional vein harvesting (CVH), no-touch, standard bridging technique (SBT) and endoscopic vein harvesting (EVH) techniques. We investigated safety and long-term efficacy outcomes. All outcomes were analyzed using the frequentist network meta-analysis. A total of 6480 patients from 34 RCTs were included. For safety outcomes, EVH reduced 91% and 77% risk of wound infection compared to no-touch and CVH, respectively. EVH and SBT also significantly reduced the risk of sensibility disorder and postoperative pain. The techniques were not significantly different regarding long-term efficacy outcomes, including mortality, myocardial infarction and graft patency. For GSV harvesting for CABG, EVH techniques are the most favorable, but in case of using an open technique, no-touch is more recommended than CVH. More effective and safer procedures should be investigated for GSV harvesting in CABG.

Acute shear stress and vein graft disease

The long saphenous vein is commonly used in cardiac surgery to bypass occluded coronary arteries. Its use is complicated by late stenosis and occlusion due to the development of intimal hyperplasia. It is accepted that intimal hyperplasia is a multifactorial inflammatory process that starts immediately after surgery. The role of acute changes in haemodynamic conditions when the vein is implanted into arterial circulation, especially shear stress, is not fully appreciated. This review provides an overview of intimal hyperplasia and the effect of acute shear stress changes on the activation of pro-inflammatory mediators.

Newly Developed Graft Failure Detected Using Computed Tomography Within 1 Year After Coronary Artery Bypass Grafting Surgery: One Single-Center Experience

Background

Newly developed graft failure negatively affects the short- and long-term outcomes of patients who experience coronary artery bypass grafting (CABG) surgery. This study explored the value of transit time flow measurement (TTFM) parameters for predicting the risk of newly developed graft failure that occurs within 1 year after CABG, as well as investigated the relationship between newly developed graft failure and adverse cardiovascular events.

Methods

A total of 134 patients who underwent CABG and had CT angiography (CTA) data (1 year post-operatively) were divided into two groups: the patient group, in which patients did not have newly developed graft failure, and the occluded group, in which patients developed newly developed graft failure between 1 and 12 months after CABG. The patency rate of grafts in different targets was analyzed. The correlations between graft failure and TTFM parameters and between graft failure and the occurrence of adverse cardiovascular events were investigated.

Results

The overall rate of newly developed graft failure was 7.2%, the venous graft failure was 10.8%, and the arterial graft failure was 0.7%. The occluded group had a higher pulse index (PI) (2.9 vs. 2.4, P = 0.007), a lower mean graft flow (MGF) (20 vs. 25 ml/min, P = 0.028), and a lower diastolic flow fraction (DF) (63.5 vs. 70%, P = 0.019) than the patent group. The cut-off value for predicting newly developed graft failure was PI > 2.75 (P = 0.007), MGF < 23.5 ml/min (P = 0.03), and DF < 65.5% (P = 0.019). Compared with the patent group, the newly developed graft failure group had higher rates of recurrent angina (13.6 vs. 0.9%, P = 0.0014) and revascularization intervention (9.1 vs. 0% P = 0.026). However, there were no differences in death, cardiac death, myocardial infarction, and cerebral infarction after CABG operation between these two groups (P > 0.05).

Conclusions

A high PI and low MGF and DF are risk factors for newly developed graft failure. The patients with newly developed graft failure had higher rates of recurrent angina and revascularization intervention. TTFM parameters may be used to predict the occurrence of newly developed graft failure in patients after CABG surgery.

Procedure and Clinical Success of Drug-Coated Balloon Fistuloplasty of the Drainage Vein in Dysfunctional Native Arteriovenous Fistulas

Purpose

Native arteriovenous fistulas (AVFs) are the most effective vascular access (VA) for haemodialysis. We aimed to evaluate the results of balloon angioplasty (fistuloplasty) from drainage vein performed for the treatment of AVF dysfunction in haemodialysis patients and examine potential patient and AVF-associated factors that might affect such results.

Methods

This is a nonrandomized, retrospective, and single-centred study. A total of 105 balloon fistuloplasties were performed for dysfunctional AVFs of 82 haemodialysis patients. Patients were treated with a drug-coated balloon according to standard procedures. Evaluations were performed by physical examinations and if needed by color Doppler imaging in every 6 months. The primary endpoint was patency by balloon fistuloplasty. Patency was evaluated clinically by detecting the thrill in AVF and by the adequacy of the dialysis. Multidimensional scaling (MDS) technique was used as a method for the statistical analysis.

Results

The success of the procedure after the first attempt was 85.3% with 70 patients. Patency in the 6th, 12th, 18th, and 24th months were 63 (76.8%), 60 (73.1%), 53 (64.6%), and 44 (54%), respectively. The procedure was considered successful when the thrill was detected in AVF and when dialysis was adequate. The statistical analysis by MDS revealed that patients' age was the most effective factor acting on the procedure success followed by the age of AVF. Other patient-associated and AVF-associated factors were not found as effective statistical evaluation.

Conclusions

Haemodialysis through native AVFs with restored functionality contributes positively to the life span and the quality of life of the patient. Probably, advanced age and high fistula age are unfavourable factors leading to the development of neointimal hyperplasia and venous stenosis. Balloon fistuloplasty of the draining vein is an effective and safe method regardless of patient age and the age of AVF.

Therapeutic-Dose Warfarin (International Normalized Ratio >1.6) Plus Aspirin Improved Long-Term Patency of Saphenous Vein Graft without Bleeding Complication

Purpose: Saphenous vein graft (SVG) is the most commonly used conduits in coronary artery bypass grafting (CABG), but the disadvantage of SVG is its tendency for progressive failure. We hypothesized that therapeutic-dose warfarin (international normalized ratio [INR] >1.6) plus aspirin improve SVG patency. This study aimed to evaluate the factors contributing to SVG patency.

Methods: Since 2010–2020, 199 patients who underwent isolated CABG using SVG were divided into two groups according to their INR values in the first year: group T (INR >1.6) and group L (INR <1.6).

Results: Group T had 162 SVGs (105 patients) and group L had 151 SVGs (94 patients). The 1-, 4-, and 7-year SVG patency rates were higher in group T than in group L (99%, 96%, and 92% vs. 93%, 86%, and 79%, respectively; p = 0.00378). The 1-, 4-, and 7-year freedom from repeat-revascularization was higher in group T than in group L (100%, 100%, and 99% vs. 98%, 95%, and 87%, respectively; p = 0.0264). Multivariate analysis showed that therapeutic-dose warfarin (p = 0.00204) and target vessel diameter (p <0.0001) were independent risk factors of SVG occlusion.

Conclusion: Therapeutic-dose warfarin (INR >1.6) plus aspirin after CABG improved the long-term patency of SVG and decreased repeat-revascularization rate.

Monitoring Cellular Proliferation, Migration, and Apoptosis Associated with Atherosclerosis Plaques In Vitro

Bromodeoxyuridine/5-bromo-2'-deoxyuridine (BrdU) is a nucleoside analog of thymidine and its incorporation into DNA during replication within S-phase of the cell cycle is used to quantify cell proliferation. Quantification of incorporated BrdU is considered the most direct measure of cell proliferation, and here we describe BrdU incorporation into cultured vascular smooth muscle cells (VSMCs) and endothelial cells in vitro. Incorporation of fluorescent-labeled ethynyldeoxyuridine/5-ethynyl-2'-deoxyuridine (EdU) is a novel alternative to BrdU assays and presents significant advantages. This method of detection of EdU based on a simple "click" chemical reaction, which covalently bonds EdU to a fluorescent dye is also outlined in this chapter with a protocol for quantitative analysis of EdU incorporation using a Fiji-based macro. We also describe how proliferation can be assessed by quantification of classical proliferative markers such as phopsho-Ser807/811 retinoblastoma (Rb), proliferating cell nuclear antigen (PCNA) and cyclin D1 by Western blotting. As these markers are involved in different aspects of the cell cycle regulation, examining their expression levels can not only reveal the relative population of proliferating cells but can also improve our understanding of the mechanism of action of a given treatment or intervention. The scratch wound assay is a simple and cost-effective technique to quantify cell migration. A protocol which involves creating a wound in a cell cultured monolayer and measuring the distance migrated by the cells after a predefined time period is also described. Gap creation can also be achieved via physical cell exclusion where cells are seeded in distinct reservoirs of a cell culture insert which reveal a gap upon removal. Cell migration may then be quantified by monitoring the rate of gap closure. The presence of cleaved caspase-3 is a marker of programmed cell death (apoptosis). To detect cleaved caspase-3 in vitro, immunocytochemistry and fluorescence can be performed as outlined in this chapter.

Ticagrelor versus aspirin and vein graft patency after coronary bypass: A randomized trial

BACKGROUND

Antiplatelet therapy prevents saphenous vein graft (SVG) occlusion and improves outcomes after coronary artery bypass graft surgery (CABG). However, the optimal postoperative antiplatelet regimen remains unclear. The goal of the Ticagrelor Antiplatelet Therapy to Reduce Graft Events and Thrombosis (TARGET) trial was to assess whether early postoperative ticagrelor reduces SVG occlusion compared to conventional aspirin therapy.

METHODS

In this multi-center double-blind randomized trial, 250 patients who had CABG with SVG were randomized to receive either aspirin 81 mg twice daily or ticagrelor 90 mg twice daily. The primary outcome was SVG occlusion at 1 year.

RESULTS

Altogether, 123 patients were randomized to aspirin and 127 received ticagrelor. One-year graft assessment was performed in 202 patients (80.8%), examining 588 grafts, yielding an overall graft occlusion rate of 10.9%. The primary outcome, SVG occlusion at 1 year, did not significantly differ between the two groups (17.4% vs. 13.2%, aspirin vs. ticagrelor, p = .30). The incidence of vein grafts with any disease (stenosis or occlusion) did not significantly differ between the groups (21.5% vs. 22.3%, aspirin vs. ticagrelor, p = .90), and the number of patients with vein graft disease did not significantly differ between the groups (29.4% vs. 28.0%, aspirin vs. ticagrelor, p = .88). Freedom from major adverse cardiovascular events at 1 year was similar between the groups (p = .60).

CONCLUSIONS

Compared to conventional aspirin therapy, ticagrelor did not significantly reduce vein graft occlusion 1 year after CABG. Further study will assess the impact of ticagrelor on 2-year graft patency for this cohort.